This sounds absolutely wrong to me. (Though note - I'm not a complexity theorist.)

For one thing, the proof of P!=NP (which is what most people assume) will almost certainly provide us a lot of new math and insight. So yes, there won't necessarily be something new practically just from the result P!=NP, because this is what everyone assumes, but it's likely to yield lots of new math.

As for the case where P=NP - that's almost certainly a gamechanger, especially if this is proved by way of a counterexample, e.g. a problem in NP that is actually computable in P. While this may not be immediately computable on current hardware, at that point we'll almost certainly focus a lot of time and effort into making it more feasible.

What CS problem do you think is more important?